Study On Detecting Method And Analysis Of Milk Flavor In UHT Pure Milk

In recent years, there was turbulence in our country dairy manufactoris. There had been manytrust crisis cases recently, which made consumers begin to challenge the quality and safety of dairyproducts and people paid more attention to pure milk which occupied categorical position in dairyproduct markets. In current time, the variety and stand of pure milk were various and some productsattracted consumers which was observably marked 'special thick milk' and 'incense thick milk'. Itwas investigation that many dairy product manufactories were against regulations to add milkflavors to the pure milk in order to balance milk source supply deficit because of different seasons,uneven milk source quality, meet the chase of 'incense' and 'thick' taste for pure milk of consumerswho were misguided long-term. In our country, although it was definitely regulated that anyadjuvant was not permitted to add to the pure milk by active dairy production standard, it was verydifficult to monitor and manage dairy product manufactoris practically for the default of correlatedetecting methods and nation detecting standard. In addition, many unlawful merchantsmanufactured imitation milk using milk flavors, water and thickening agents, which severelythreatened the health of people. In this research, advanced modern analytical apparatus—gaschromatogram/mass spectrum were utilized to analyze the aroma components of different marketmilk flavors, and searched the mark indicators of evaluating milk flavors in pure milk. The effectiveextract method was established according to the physical chemistry character of flavor indicators.Then qualitative and quantitative methods were established for flavor indicators in pure milk byGC/MS.In this research, through the investigation of 4 different liquid milk flavors and 4 differentpowder milk flavors, it was possible that the dehydrated alcohol dilution of liquid milk flavorscould be analyzed by GC/MS and 0.25% was confirmed as the best dilution ratio; the organicsolvent extraction of powder milk flavors could be analyzed by GC/MS and ether was the bestextraction agent. The reproducibility and stability of analytical methods were considered and RSDvalue was between 1.12% and 9.67%, which could meet analytical request. The components ownedby liquid milk flavors wereδ-Decalactone,δ-Dodecalactone and Ethyl maltol; The componentsowned by powder milk flavors wereδ-Undecalactone and Vanillin.By referring to records, it was known that kettle boil flavor, sterilization flavor, oxidationflavor and inherent UHT milk flavor were the flavor characteristic of UHT pure milk. There weresulfur-containing substance such as hydrogen sulfide, sulfhydryl methane and DMS; fatty acidoxidation and Maillard's reaction productions such as aldehyde, propanal, N-valeraldehyde, caproaldehyde, Butanone, pentanone, 2-nonanone, 2-octanone, 2-heptanone and 2-undecanone; theadvanced Maillard's reaction productions such as 2,6-methylpyrazine, 2-ethylpyrazine,benzothiazole,δ-decalactone andδ-dodecalactone. Comprehending the character results of UHTmilk flavor and milk flavors components, Ethyl maltol and Vanillin were determined as the flavorindicators for evaluating UHT milk that was added milk flavors.When pH exceeded 8, Ethyl maltol and Vanillin existed by phenolate form which could depletethe effects on milk fat; when pH was between 2 and 6, they existed by neutral molecule, they wereextracted by ether. Through simple alkali treatment and extraction by organic solvent, the objectscould be effectually extracted, which was easy to pervasion, depleted the difficulty of demandingfor special pre-processing equipments.The quantitative analysis of flavor indicators were completed by GC-MS/SIM, whichconsumedly improved sensibility; m/z 97, 125, 140 were determined as select ions and m/z 140 wasquantitative ion; m/z 109, 123, 152 were determined as select ions and m/z152 was quantitative ion.The detecting limit of this method was 0.006μg/g and the recovery rate was between 80% and 95%;RSD of precision was little 7%. The investigation for 14 different market UHT milk werecompleted by the method and the results were acquired that the detection rate of Ethyl maltol was42.68%, the detection rate of Vanillin was 64.28%, the non-detection rate of flavor indicators was21.41%.